This invention relates generally to ribbon spools and, more particularly, is directed to a universal typewriter ribbon spool.
Generally, typewriter ribbon spools for the various brands of typewriters are each constructed differently. The reason for such differences resides basically in the mechanism used on the typewriter for engaging the spool. Generally, all typewriters utilize a central spindle which is coaxially aligned within the spool by tabs that engage respective spaced apertures in one of the flange members of the spool. However, with different brands, the tabs are spaced differently, and even the spindles are constructed with different diameters. An example of one such typewriter that uses such spools is the Underwood Typewriter.
Another arrangement that is used by Olivetti employs a threaded spindle inserted coaxially within the spool and a nut arrangement at the opposite side of the spool for threadedly engaging with the spindle. This design also has a plurality of the aforementioned spaced tabs which engage within respective apertures in the flange member at the side of the nut arrangement. With this latter arrangement, the spindle is constructed with a different diameter than those of the aforementioned typewriter designs.
Accordingly, a manufacturer of spools for different typewriters must necessarily provide different molds and dies for making the different spools. This is costly and inefficient.
It has therefore been proposed to provide a universal spool which can be used with a plurality of different styles of typewriters.
For example, U.S. Pat. No. 3,042,180 discloses a universal typewriter ribbon spool having an insert or adapter mounted within the central hub thereof. According to the second embodiment of this patent, the adapter is formed with four arms which carry four arcuate sections, respectively, forming a cylindrical split sleeve coaxially positioned in the adapter. The arms and sections terminate at their upper ends in a common plane positioned at about one-third the distance down from the upper end of the side wall of the adapter and terminate at their lower end slightly above the lower end of the side wall. With this embodiment, the sections frictionally receive a spindle, referred to as the S type in the patent. For reduced diameter spindles which are not frictionally engaged by the sections, that is, for type S" spindles described in the patent, a nut is threaded down on the threaded top of the spindle S" such that the upper portion of the nut exerts a downward pressure on the upper side of the top closure of the spool.
U.S. Pat. No. 2,873,839 also discloses resilient arms as part of the insert of a universal typewriter ribbon spool having arcuate sections at the free ends thereof which are coaxially positioned within the insert for frictionally engaging the spindle.
U.S. Pat. No. 3,819,027 also discloses a multiple utility ribbon spool having an insert which can be used with various spindles.
In U.S. Pat. No. 3,833,109, a rolled tubular hub or sleeve about which the ribbon is wrapped is positioned over the hub of the spool, the latter having edges to maintain the rolled tubular hub thereon in a fixed relation. In a like manner, U.S. Pat. No. 2,476,928 uses a keyway and key arrangement to fix the sleeve on the central hub.
Other patents relating generally to the subject matter of the present invention, but far less pertinent than those discussed above, include U.S. Pat. Nos. 1,991,435; 2,925,164; 3,045,800; 3,094,204; 3,295,655; and 3,807,544.
The present invention is designed to provide a novel universal typewriter ribbon spool which differs structurally from the aforementioned spools and provides an advantageous assembly thereover.